Using Swift 3, Xcode 8.2.1
Method:
func moveToNextTextField(tag: Int) {
print(tag)
}
The lines below compile fine, but tag
has an uninitialized value:
let selector = #selector(moveToNextTextField)
Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: selector, userInfo: nil, repeats: false)
However, I need to pass a parameter. Below fails to compile:
let selector = #selector(moveToNextTextField(tag: 2))
Swift Compile Error:
Argument of #selector does not refer to an @objc method, property, or initializer.
How can I pass an argument to a selector?
#selector
describes method signature only. In your case the correct way to initialize the selector is
let selector = #selector(moveToNextTextField(tag:))
Timer has the common target-action mechanism. Target is usually self and action is a method that takes one parameter sender: Timer
. You should save additional data to userInfo
dictionary, and extract it from sender
parameter in the method:
func moveToNextTextField(sender: Timer) {
print(sender.userInfo?["tag"])
}
...
let selector = #selector(moveToNextTextField(sender:))
Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: selector, userInfo: ["tag": 2], repeats: false)
You cannot pass a custom parameter through a Timer
action.
Either
#selector(moveToNextTextField)
...
func moveToNextTextField()
or
#selector(moveToNextTextField(_:))
...
func moveToNextTextField(_ timer : Timer)
is supported, nothing else.
To pass custom parameters use the userInfo
dictionary.
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